[PropertyInfo] Mentioned the phpDoc collection type

Author: javiereguiluz

components/property_info.rst

@@ -315,9 +315,15 @@ a collection - a non-scalar value capable of containing other values. Currently
 this returns ``true`` if:
 
 * The :ref:`built-in PHP data type <components-property-info-type-builtin>`
-  is ``array``, or
+  is ``array``;
 * The mutator method the property is derived from has a prefix of ``add``
-  or ``remove`` (which are defined as the list of array mutator prefixes).
+  or ``remove`` (which are defined as the list of array mutator prefixes);
+* The phpDocumentor annotation is of type "collection" (e.g.
+  ``@var Iterator<DateTime>``, ``@var \Iterator<integer,string>``, etc.)
+
+.. versionadded:: 4.2
+
+    The support of phpDocumentor collection types was introduced in Symfony 4.2.
 
 Type::getCollectionKeyType() & Type::getCollectionValueType()
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~